Department of Maternal-Fetal Medicine, Royal Womens Hospital, Melbourne, Victoria, Australia.
Department of Maternal-Fetal Medicine, Royal Womens Hospital, Melbourne, Victoria, Australia; Department of Obstetrics and Gynaecology, University of Melbourne, Melbourne, Victoria, Australia.
Am J Obstet Gynecol. 2016 Feb;214(2):172-191. doi: 10.1016/j.ajog.2015.10.930. Epub 2015 Nov 6.
The mechanisms responsible for twinning and disorders of twin gestations have been the subject of considerable interest by physicians and scientists, and cases of atypical twinning have called for a reexamination of the fundamental theories invoked to explain twin gestations. This article presents a review of the literature focusing on twinning and atypical twinning with an emphasis on the phenomena of chimeric twins, phenotypically discordant monozygotic twins, mirror-image twins, polar body twins, complete hydatidiform mole with a coexistent twin, vanishing twins, fetus papyraceus, fetus in fetu, superfetation, and superfecundation. The traditional models attributing monozygotic twinning to a fission event, and more recent models describing monozygotic twinning as a fusion event, are critically reviewed. Ethical restrictions on scientific experimentation with human embryos and the rarity of cases of atypical twinning have limited opportunities to elucidate the exact mechanisms by which these phenomena occur. Refinements in the modeling of early embryonic development in twin pregnancies may have significant clinical implications. The article includes a series of figures to illustrate the phenomena described.
导致双胞胎和双胞胎妊娠异常的机制一直是医生和科学家关注的焦点，而非典型双胞胎的病例需要重新审视用于解释双胞胎妊娠的基本理论。本文回顾了文献，重点关注了双胞胎和非典型双胞胎，强调了嵌合体双胞胎、表型不一致的同卵双胞胎、镜像双胞胎、极体双胞胎、共存双胞胎的完全性葡萄胎、消失的双胞胎、纸样胎儿、胎中胎、超期妊娠和多胎妊娠等现象。本文对将单卵双胞胎归因于分裂事件的传统模型和最近描述单卵双胞胎为融合事件的模型进行了批判性回顾。对人类胚胎进行科学实验的伦理限制以及非典型双胞胎病例的罕见性限制了阐明这些现象发生的确切机制的机会。双胞胎妊娠中早期胚胎发育模型的改进可能具有重要的临床意义。本文还包括一系列图片来说明所描述的现象。
